Milligrams to Grams Converter

Exactly 1000. The gram is the SI base reference for mass at the kilogram scale, and the milligram is defined as one-thousandth of a gram (the prefix milli- means 10^-3). So 1 g = 1000 mg, 0.5 g = 500 mg (a standard acetaminophen tablet), and 0.001 g = 1 mg. Going the other way, divide milligrams by 1000 to get grams: 250 mg = 0.25 g, 2500 mg = 2.5 g. The relationship is exact by definition, not an approximation, so no rounding error is ever introduced when you convert between mg and g.

Exactly 1000 micrograms (mcg or ug) per milligram, and 1,000,000 mcg per gram. The microgram is one-millionth of a gram (the prefix micro- means 10^-6). The unit shows up almost exclusively in pharmacology and nutrition for very small doses: 1000 mcg of vitamin B12, 400 mcg of folic acid in prenatal vitamins, or 25 mcg of a thyroid hormone like levothyroxine. The abbreviation mcg is preferred on US drug labels because the Greek letter mu (in ug) can be misread as m, which would multiply the dose by 1000 with potentially fatal consequences. The ISMP and Joint Commission both recommend mcg over ug for clinical use.

Milligrams keep many medication quantities readable without long decimals. Smaller quantities may be labeled in micrograms, while larger quantities may be labeled in grams. Always follow the unit and strength printed on the specific medication label because products and prescribed doses vary.

Labels use micrograms when a milligram value would be an awkward decimal. International Units are different because they measure biological activity, and their mass conversion is specific to the substance and form. Read the Supplement Facts panel and do not use one vitamin's IU conversion for another.

A metric tonne (sometimes spelled metric ton, abbreviated t) is exactly 1000 kg, or 2,204.62 lb. A US short ton is 2,000 lb, which is about 907.18 kg, so the metric tonne is roughly 10 percent heavier. The UK also has a long ton at 2,240 lb (about 1,016 kg), but this is rare in everyday use. Shipping, freight, and international trade run on metric tonnes; US construction, mining, and HVAC (air conditioning capacity) still use short tons. If a spec sheet says "5 tons" you have to read context to know which one is meant. This converter always uses the metric tonne (1000 kg = 1,000,000 g) for consistency with the SI scale.